Hydraulic pressurization system

ABSTRACT

The present invention relates to a hydraulic pressurization system, in particular for application to pressurization devices operating in accordance with the high hydrostatic pressure principle. In particular, the present invention provides a pressurization system for modifying the pressure in a pressurization device. The system comprising a first hydraulic circuit in which one or more primary pressure accumulators are connected to the pressurization device in controlled manner in order to permit a substantially incompressible fluid to be admitted to and removed from the pressurization device at a first pressure, the primary pressure accumulators being precompressed-gas pressure accumulators.

FIELD OF THE INVENTION

The present invention relates to a hydraulic pressurization system, inparticular for application to pressurization devices operating inaccordance with the high hydrostatic pressure principle.

BACKGROUND ART

The present Applicant's published European patent application No. EP 1048 608 describes apparatus for continuous sterilization of packagedfoodstuffs which comprises a treatment, at high hydrostatic pressure, ofbeverages previously introduced into containers made of deformablematerial (for example, polyethylene terephthalate) which are sealedbefore treatment. The containers are introduced into suitablepressurization chambers which are then filled with a substantiallyincompressible liquid such as water and in which the hydrostaticpressure is imparted by a piston provided with a pressure-multiplier.The piston is driven by a mechanical device comprising a cam andoperated by a motor.

However, in order to be able to perform an effective sterilizationcycle, which in turn comprises pressurization and partialdepressurization stages in succession, within the short time required bya continuous operation such as that described in the above-mentionedEuropean patent application, the system for transmitting the pressurefrom the actuator to the piston must be extremely efficient, in otherwords, the time elapsing between the energization of the actuator andthe reaching of the desired pressure inside the pressurization chambermust be as short as possible. A mechanical system such as that describedabove does not fully comply with these requirements.

SUMMARY OF THE INVENTION

The problem underlying the present invention is therefore to provide apressurization system which solves the problems of the devices of theprior art, in particular which permits quick and effectivepressurization.

This problem is solved by a pressurization system as defined in theappended claims.

Further characteristics and advantages of the pressurization system ofthe present invention will become clearer from the description of twopreferred embodiments, given below by way of non-limiting example, withreference to the following drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially-sectioned, schematic view of the pressurizationsystem according to the present invention,

FIG. 2 is a partially-sectioned, schematic view of a second embodimentof the pressurization system of the present invention, and

FIG. 3 is a partially-sectioned, schematic view of a detail of thepressurization system of the invention, in accordance with a thirdembodiment.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIG. 1, the pressurization system, generally indicated1, acts on a high hydrostatic-pressure pressurization device 2comprising a housing 3 which has a removable closure element 4 andinside which a pressurization chamber 5 is defined for housing one ormore objects 6, for example bottles, to be processed at high hydrostaticpressures. A piston 7, acting inside the pressurization chamber 5, has aT-shaped cross-section the larger-diameter end of which defines,together with the walls of the housing 3, a chamber 8 filled with asubstantially incompressible fluid which, in the embodiment described,is hydraulic oil. A duct (not shown in the drawing), extendingthroughout a wall of the housing 3 which defines the chamber 8, isconnected to the pressurization system of the present invention by meansof a tube 9 which admits the hydraulic oil to the chamber 8 at highpressure. An example of a pressurization device to which thepressurization system of the present invention may advantageously beapplied is that described in the European patent application No.00830705.0 which was filed on 26th Oct. 2000 in the name of theApplicant of the present patent application and the description of whichis incorporated herein by reference.

Turning now to the description of the pressurization system of thepresent invention, the tube 9 is connected, by means of respective tubeconnectors 9 a, 9 b, 9 c, 9 d, 9 e, to a plurality of primary pressureaccumulators 10 a, 10 b, 10 c, 10 d, 10 e, which are filled withhydraulic oil for part of their volumes, the remaining part of theirvolumes being occupied by an inert gas, for example nitrogen, underpressure. The pressure to which the gas is subjected in the reservoirsis preferably approximately 300 bar.

Interposed in the path of the tube 9 from the primary pressureaccumulators 10 a, 10 b, 10 c, 10 d, 10 e to the pressurization device 2are direct-pressurization valve means 11, for example, a solenoid valvethe opening of which enables the pressure stored by the precompressedgas in the accumulators to be discharged onto the piston 7 of thepressurization device 2, as will be described further below.

A pump 12, drawing hydraulic oil from a reservoir 13 and admitting it tothe tubing circuit 9, 9 a, 9 b, 9 c, 9 d, 9 e through a charging tube14, keeps the primary pressure accumulators 10 a, 10 b, 10 c, 10 d, 10 eunder pressure. In this case also, there are interposed in the path ofthe tube 14 from the pump 12 to the connection with the tube 9,charging-valve means 15, for example, a solenoid valve with open/shutcontrol and, downstream thereof, a non-return valve 16, the function ofwhich is to prevent the excess pressure being vented from the primaryaccumulators 10 a, 10 b, 10 c, 10 d, 10 e towards the pump 12.

Downstream of the primary accumulators 10 a, 10 b, 10 c, 10 d, 10 e andupstream of the respective solenoid valve 11, the tube 9 branches into asecondary tube 17. This secondary tube 17 is connected, byindirect-pressurization valve means 18, for example, a solenoid valve,to pressure-multiplier means 19 such as a hydraulic pressure-multiplier.The valve means 18 comprises two outlets, that is, a pressurizationoutlet 29 and a discharge outlet 30, and an inlet 32, which arecontrollable separately. In particular, the means 18 may be a three-waysolenoid valve, operable in accordance with the following operativeconditions: a) completely closed, b) pressurization outlet 29 anddischarge outlet 30 in flow communication, inlet shut, c) inlet andpressurization outlet 29 in flow communication, discharge outlet 30shut. The discharge outlet 30 discharges hydraulic oil towards thereservoir 13 by means of a duct provided with valve means 31 withopen/shut control.

The pressure-multiplier 19 comprises a housing 20 made of a materialsuitable for withstanding high pressures. An example of this material isa multi-layer jacket such as that described in the above-mentionedEuropean patent application No. 00830705.0 filed on 26th Oct. 2000, thedescription of which, in particular with regard to this multi-layerjacket and the structure of the pressurization piston, is incorporatedherein by reference.

A piston 21 housed for sliding in the housing 20 has a T-shapedcross-section the larger-diameter end of which defines, together withthe walls of the housing 20, a first chamber 22 filled with hydraulicoil, into which the secondary tube 17 opens. A second chamber 23, whichin turn is filled with oil, is defined by the smaller-diameter end ofthe piston 21 and by the walls of the housing 20. The space 28 betweenthe upper shoulder of the piston 21 and the body of the housing20—which, at this point, has a thickness such as to be engaged forsliding by the smaller-diameter section of the piston,—defines thestroke of the piston 21. The chamber 23 is in fluid communication with aconnecting duct 24 which is reconnected to the tube 9 downstream of thedirect-preassurization valve means 11. A non-return valve 25 isinterposed in the connecting duct 24, upstream of the point ofconnection with the tube 9.

The tube 9 is connected, in the portion disposed between thedirect-pressurization valve means 11 and the pressurization device 2, toa duct 26 for discharging the hydraulic oil from the pressurizationdevice 2 to the oil reservoir 13. Discharge-valve means 27, for example,a solenoid valve, are interposed in the path of the discharge duct 26.

The operation of the pressurization system according to the presentinvention will now be described, still with reference to FIG. 1. Innormal operating conditions, the hydraulic apparatus of thepressurization system, that is, the tubes 9, 14, 24, 26, the chambers 8,22, 23 of the pressure-multipliers and parts of the primary pressureaccumulators 10 a, 10 b, 10 c, 10 d, 10 e, is filled with hydraulic oil.The pump 12, which draws hydraulic oil from the reservoir 13 and admitsit to the primary accumulators 10 a, 10 b, 10 c, 10 d, 10 e, underpressure, through the charging tube 14, keeps the pressure of the inertgas in these accumulators above a predetermined operating level which,in the embodiment described, is about 300 bar. The non-return valve 16prevents discharge of the pressure from the accumulators towards thepump 12.

At the beginning of a pressurization cycle, the direct-pressurizationvalve means 11, which are closed in the rest condition, open, allowingsome of the pressure accumulated in the primary accumulators 10 a, 10 b,10 c, 10 d, 10 e to be discharged instantaneously along the tube 9 andinto the chamber 8 of the pressurization device 2. During this firstpressurization stage, the indirect-pressurization valve means 18 and thedischarge-valve means 27 are closed. The first pressurization stagecontinues until the pressure in the chamber 8 is in equilibrium withthat in the accumulators. If the primary accumulators 10 a, 10 b, 10 c,10 d, 10 e are of suitable dimensions so as to be able to store apotential energy much greater than that required by the above-mentionedoperation and by that provided for in the second stage described below,the pressure in the chamber 8 will be substantially equal to the initialpressure of the gas in the accumulators, that is, in the embodimentdescribed, about 300 bar. This effect is achieved, as stated, by theprovision of a volume of precompressed gas definitely greater than thevolume of hydraulic oil entering the chamber 8 of the pressurizationdevice 2.

In any case, by causing the pump 12 to operate continuously even duringthe system-pressurization stage, it will be possible to keep thepressure in the primary accumulators 10 a, 10 b, 10 c, 10 d, 10 esubstantially stable and hence to avoid any excessive discharge of thepotential energy accumulated therein.

At this point, the second pressurization stage begins; this provides forthe closure of the direct-pressurization valve means 11 and theactivation of the indirect-pressurization valve means 18. In particular,the pressurization outlet 29 will be opened and the discharge outlet 30will be kept closed. The potential energy stored in the form ofpressurized gas in the primary pressure accumulators 10 a, 10 b, 10 c,10 d, 10 e is discharged, in this case, along the secondary tube 17 andthrough the pressure-multiplier 19 to the chamber 8 of thepressurization device 2.

The operation of the pressure-multiplier 19, like that of thepressurization device 2, is based on the presence of a piston 21 with aT-shaped cross-section. In fact, the pressure reached at the outlet ofthe pressure-multiplier 19 will be proportional to the ratio between thelower surface (in contact with the chamber 22) and the upper surface ofthe piston. For example, if the ratio between these two areas is 2, theoil pressure will be doubled, at least as a first approximation. In theembodiment described, the pressure output by the pressure-multiplier 19will therefore be about 600 bar. When the equilibrium condition isreached, the piston 7 of the pressurization device 2 will also besubject to this pressure, which will therefore be transferred, aftersuitable amplification by means of the piston 7 as described above forthe piston 21, into the pressurization chamber 5 and onto the object 6to be processed which, in the example described, is a bottle to besterilized. With suitable dimensions of the smaller and larger surfaces7 of the piston, it will be possible to achieve a pressure of a fewthousand bar in the pressurization chamber 5.

At this point, a series of partial decompressions and compressions canbe brought about simply by opening the direct-pressurization valve means11 and closing the inlet of the indirect-pressurization valve means 18(operative condition a) of the valve means 18, see above), until, as theoil flows towards the primary pressure accumulators 10 a, 10 b, 10 c, 10d, 10 e, the pressure in the chamber 8 is reduced to the desired level(for example, 500 bar); this operation will be followed by a closure ofthe direct-pressurization valve means 11 and by the simultaneous ordeferred opening (according to whether the pressure is to be kept at theintermediate level for a longer or shorter period) of theindirect-pressurization means 18 (operative condition c), see above), soas to re-establish the maximum pressure (in the example described, 600bar). This sequence of operations may be repeated in order to implementthe desired pressurization cycle. Naturally, during the partialdecompression stages provided for herein, the potential energy of thesystem will be recovered by discharge of the excess pressure to theaccumulators, as will be described fully below.

Upon completion of the second pressurization stage outlined above, thedecompression stage, which in turn is composed of two distinct stages,will start. During the first stage, the discharge-valve means 27 and theindirect-pressurization valve means 18 will remain closed (operativecondition a), see above), whilst the direct-pressurization valve means11 will be opened. Owing to the difference between the pressuresexisting in the primary pressure accumulators 10 a, 10 b, 10 c, 10 d, 10e (about 300 bar in the example described) and in the chamber 8 of thepressurization device 2 (about 600 bar in the example described) thehydraulic oil will thus flow in the opposite direction to that in whichit flowed in the pressurization stage, so as to compress the gas in theaccumulators until equilibrium is reached, that is, until the chamber 8is decompressed to the equilibrium pressure of 300 bar. The non-returnvalve 25 will enable the pressure-multiplier 19 which, in this case,would operate in reverse, to be bypassed. The device thus clearlypermits at least partial recovery of the potential energy expended inthe compression of the fluid to 600 bar in the chamber 8.

When equilibrium with the pressure in the primary accumulators 10 a, 10b, 10 c, 10 d, 10 e has thus been reached, further decompression from300 bar to atmospheric pressure does not permit recovery of energy whichis therefore discharged along the discharge tube 26, after closure ofthe pressurization-valve means 11 and opening of the discharge-valvemeans 27.

It will also be necessary to re-establish atmospheric pressure in thechamber 22 of the pressure-multiplier 19. This condition is achieved bymoving the valve means 18 to operative condition b) described above andopening the discharge-valve means 31. It should be noted that thepressure can be discharged from the chamber 22 of the multiplier at anymoment during the entire decompression stage described above.

The entire process is controlled by an operating and control unit (notshown in the drawings), normally of the electronic type, which providesfor the opening and closure of the valve means, the operation of thepump 12, and for any other additional operations such as those requiredby the particular application to which the pressurization system of thepresent invention is dedicated. In the embodiment shown in the drawings,these operations may relate to the closure and opening of the closureelement 4 of the pressurization device 2, to the insertion or removal ofthe bottle 6, and to monitoring of temperature, pressure or any otheroperative conditions required. Examples of these additional operationsare those described in the above-mentioned European patent applicationNo. 00830705.0 filed on Oct 26, 2000.

The embodiment of the present invention shown in FIG. 2 differs from thefirst embodiment described above in the provision of a third hydrauliccircuit entrusted with performing some auxiliary functions of thesystem, in particular, the resetting of the piston 21 of thepressure-multiplier 19, that is, its return to its initial position uponcompletion of the pressurization cycle. In FIG. 2, reference numeralsthe same as those indicated in FIG. 1 correspond to the same parts ofthe system. The pressurization system will therefore be described onlywith reference to the additional characteristics, the foregoingdescription remaining the same for the rest of the system.

The charging-valve means 115 disposed downstream of the pump 12 havethree separately controllable outlets. The first outlet is connected tothe charging tube 14, as described above. A second outlet is in fluidcommunication with a secondary charging tube 128 which in turn isconnected to a secondary pressure accumulator 129. A non-return valve130 is disposed upstream of this accumulator. A third outlet is in fluidcommunication with a recirculation duct 131 which returns the hydraulicoil to the pump when the other two outlets of the valve means 115 areclosed. This arrangement enables the pump 12 always to be kept inoperation throughout the operation of the system, avoiding constantstarting and stopping which are detrimental to the operation of thepump.

The secondary accumulator 129 is just the same as the primaryaccumulators 10 a, 10 b, 10 c, 10 d, 10 e described above, with the solepossible difference that the pressure of the gas compressed inside itmay be kept lower than that of the primary accumulators because of thelower energy normally required by the auxiliary operations to which thesecondary accumulator is dedicated. In the example described, thispressure is about 150 bar.

The secondary charging tube 128 is in fluid communication, in theportion between the non-return valve 130 and the secondary accumulator129, with an auxiliary tube 132 which opens inside thepressure-multiplier 19 in the space 28 which defines the stroke of thepiston 21. Interposed in this auxiliary tube 132 are valve means 133with open/shut control and, downstream thereof, a non-return valve 134.A discharge tube 135 provided with a non-return valve 136, puts thespace 28 into flow communication with the tube connected to thedischarge outlet 30 of the valve means 18, upstream of the valve means31.

The operation of the pressurization system according to the embodimentof FIG. 2 is exactly the same as that described above for the firstembodiment. At the accumulator-charging stage, the charging-valve means115 will keep the outlets towards the tubes 14 and 128 open whilst theoutlet towards the recirculation duct 131 will remain closed. Thepressurization-valve means 133, as well as the means 11, will be closed.During the pressurization stage already described above, the valve means133 of the auxiliary tube 132 will remain closed whilst the valve means31 will be in the open condition. As already described, at this stage,the secondary pressurization-valve means 18 will be either in operativecondition a) (first pressurization stage) or in operative condition c)(second pressurization stage). Upon completion of the pressurizationcycle described above, the valve means 31 will be closed and the valvemeans 133 will be opened and will provide for the admission of oil underpressure to the space 28, causing the piston to return to its startingposition. Upon completion of this operation, the valve means 31 will beopened and the valve means 18 will be put in operative condition b),enabling the pressure accumulated in the chamber 22 and in the space 28of the pressure-multiplier 19 to be discharged.

As stated above, the pump 12 advantageously operates continuously duringthe period for which the plant is in operation. The system of thepresent invention may advantageously comprise pressure sensors fordetecting the pressure in the primary pressure accumulators 10 a, 10 b,10 c, 10 d, 10 e and in the secondary accumulator 129. These pressuresensors send a signal to the operating and control unit that controlsthe outlets of the valve means 115 which are connected, respectively, tothe charging tube 14, to the secondary charging tube 128, or to therecirculation duct 131. For example, when the pressure in the primaryaccumulators 10 a, 10 b, 10 c, 10 d, 10 e reaches the pressure set (inthe embodiment described, about 300 bar), the outlet of the valverelating to the tube 14 is thus blocked. Similarly, when the desiredpressure of about 150 bar is reached in the secondary accumulator 129,the outlet for the tube 128 is blocked. When both of the outlets for thetubes 14 and 128 are closed, the operating and control unit provides forthe outlet to the recirculation duct 131 to be opened. The system of theinvention thus enables the pressure in the pressure accumulators to bekept almost constant, without the need to interrupt the operation of thepump 12, even during the stage of the pressurization of thepressurization device 2.

As shown in FIG. 3, according to a further embodiment, the secondaryhydraulic circuit connected to the secondary pressure accumulator 129also operates the mechanism for opening and closing the pressurizationdevice 2.

With regard to the description of the pressurization device 2, inparticular with regard to the structure of the closure element 4 and itsopening and closure mechanism, specific reference is made here to thedescription of the above-mentioned European patent application No.00830705.0 filed on 26th Oct. 2000, which is incorporated herein byreference. The closure element 4 is a cylinder with a transversethrough-hole for the insertion of a pin 136. The pin 136 also extendsthrough the wall of the housing 3 of the device and has the function ofa lock for the closure element 4 so as to cope with the axial thrusts ofthe system. The pin 136 constitutes the shaft of a piston 137 housed forsliding in a housing 138 of the pin piston. The piston 137 defines, inthe housing 138, a return chamber 140 (which the surface of the pistoncarrying the pin 136 faces) and a thrust chamber 139 (which the oppositesurface of the piston faces). The closure element 4 is fixed at the topto a shaft 141 which in turn terminates, at its opposite end, in apiston 142 housed for sliding in a housing 143 of the closure piston. Inthis case also, the piston 142 defines in the housing 143, a returnchamber 144 (which the surface of the piston carrying the shaft 141faces) and a thrust chamber 145 (which the opposite surface of thepiston faces).

In this embodiment, the valve means 133 connected to the secondarypressure accumulator 129 will have three outlets. The first outlet isconnected to the secondary tube 132, as described above. The secondoutlet is in fluid communication, by means of a duct 146, withclosure-control valve means 147. The third outlet is in fluidcommunication, by means of a duct 148, with pin-control valve means 149.The three outlets are operable independently.

The closure-control valve means 147 in turn have two outlets. The firstoutlet is connected to a thrust tube 150 which brings hydraulic oil tothe thrust chamber 145 of the closure-piston housing 143. The secondoutlet is connected to a return tube 151 which brings hydraulic oil tothe return chamber 144 of the closure-piston housing 143.

Similarly, the pin-control valve means 149 has two outlets. The firstoutlet is connected to a thrust tube 152 which brings hydraulic oil tothe thrust chamber 139 of the pin-piston housing 138. The second outletis connected to a return tube 153 which brings hydraulic oil to thereturn chamber 140 of the pin-piston housing 138.

Both the thrust tubes 150, 152 and the return tubes 151, 153 are in flowcommunication with respective ducts which recirculate the oil to thereservoir 13. Each of these ducts has valve means (not shown in thedrawing) which open and close alternately.

For example, during the closure of the closure element, the sequence ofoperations will be as follows. The outlet of the valve means 133 to theduct 146 is opened and, at the same time, the closure-control valvemeans 147 open the outlet to the thrust tube 150 which admits oil to thethrust chamber 145. The oil present in the return chamber 144 willtherefore be pumped along the return tube 151 by the piston and, findingthe valve means 147 closed, will be directed into the duct whichrecirculates the oil to the reservoir 13, the valve of which willtherefore be in the open condition.

As a result of the thrust of the oil, the closure element 4 will fallonto the opening of the housing 3 of the pressurization device 2 toblock this opening. At this point, the valve means 147 will keep both ofthe outlets in the closed condition, whilst the valve means 149 willopen the outlet for the thrust tube 152. The pin 136 will also beinserted through the holes in the casing 3 of the device and of theclosure element 4 by a mechanism similar to that described above for theclosure element 4. During this operation, the oil discharged from thereturn chamber 140 of the pin-piston housing 138 will be directed intothe respective recirculation duct towards the reservoir 13, after thevalve means connected thereto have been opened. The same sequence ofsteps will be repeated, but in reverse, for the release and removal ofthe closure element 4 upon completion of the pressurization cycle.

The advantages of the pressurization system of the present invention areimmediately clear from the foregoing description.

First of all, the system provides for the storage of potential energy inthe form of pressurized gas in the pressure accumulators and itsinstantaneous release at the moment of use by kinetics approaching thoseof a deflagration. This mechanism reduces to the minimum the timesrequired for the pressurization stage so that cycles comprisingpressurizations and partial decompressions can be performed inaccordance with predetermined profiles which are particularlyadvantageous in some applications (for example, sterilization of foodsor beverages in containers). For example, it will be possible to bringthe pressure in the chamber 8 of the pressurization device 2 fromatmospheric pressure to 600 bar in about 5 seconds, and partialdecompression to 500 bar and repressurization to 600 bar may requireonly about 2 seconds.

In the second place, the provision of a pressure-multiplier 19 which canbe operated at the pressurization stage and bypassed at thedecompression stage permits partial recovery of the potential energy,optimizing the energy cycle of the system.

The provision of the secondary pressure accumulator 129 has theadvantage that some auxiliary functions such as the resetting of thepressure-multiplier piston and the opening/closure of the closureelement of the pressurization device are also brought about by the samehydraulic system and within the same short times. For example, thislatter operation can also be carried out in a time generally of between4 and 4.5 seconds.

Finally, since the pressurization system according to the invention iscomposed substantially of a hydraulic circuit, mechanical componentry(mechanical actuators, cams, etc.) can be minimized, with a consequentreduction in the maintenance costs of the system.

Naturally, only some specific embodiments of the pressurization deviceof the present invention have been described and a person skilled in theart will be able to apply thereto all modifications necessary to adaptthem to particular applications without, however, departing from thescope of protection of the present invention.

For example, the number of primary pressure accumulators 10 a, 10 b, 10c, 10 d, 10 e may be increased or reduced according to the requirementsand the size of the plant. Similarly, it will be possible to providemore than one secondary pressure accumulator 129, in dependence on thetype and quantity of additional operations to which it is to bededicated.

1. A pressurization system for modifying the pressure in apressurization device, the system comprising a first hydraulic circuitin which one or more primary pressure accumulators are connected to thepressurization device in a controlled manner in order to permit asubstantially incompressible fluid to be admitted to, or recovered from,the pressurization device at a first pressure, and an operating andcontrol unit which governs operation of the system, wherein the primarypressure accumulators are precompressed-gas pressure accumulators andthe operating and control unit controls the operation of pumping meansand the operation of valve means, based upon readings of temperature andpressure sensors of the system.
 2. A pressurization system according toclaim 1, the system comprising a second hydraulic circuit in which theprimary pressure accumulator or accumulators are connected to thepressurization device in controlled manner by means of apressure-multiplier means in order to admit the incompressible fluid tothe device at a second pressure greater than the first pressure.
 3. Apressurization system according to claim 2, the first and secondhydraulic circuits being in flow communication with pumping means whichdraw the incompressible fluid from a reservoir and admit it to the firstand second hydraulic circuits.
 4. A pressurization system according toclaim 3 in which the pumping means are connected to the primary pressureaccumulators by means of a charging tube in which valve means withopen/shut control and, downstream thereof, a non-return valve, areinterposed.
 5. A pressurization system according to claim 2, in whichthe second hydraulic circuit comprises a secondary pressurization tubewhich originates from the primary tube and which is connected, byindirect-pressurization valve means, to the pressure-multiplier means,the pressure-multiplier means in turn being in flow communication with aconnecting duct in which a non-return valve is interposed and which isreconnected to the direct-pressurization tube downstream of the point oforigin of the secondary pressurization tube.
 6. A pressurization systemaccording to claim 5 in which the pressure-multiplier means comprises ahousing inside which a piston with a T-shaped cross-section is housedfor sliding, the larger-diameter end of the piston defining, togetherwith the walls of the housing, a first chamber which is filled with anincompressible fluid and into which the secondary pressurization tubeopens, a second chamber which, in turn, is filled with theincompressible fluid, being defined by the smaller-diameter end of thepiston and by the walls of the housing, the second chamber being influid communication with the connecting duct.
 7. A pressurization systemaccording to claim 5, in which the indirect-pressurization valve meanscomprise an inlet, a pressurization outlet in flow communication withthe first chamber of the pressure-multiplier means, and a dischargeoutlet in flow communication with a duct provided with valve means withopen/shut control, for the recirculation of the incompressible fluid tothe reservoir.
 8. A pressurization system according to claim 7 in whichthe indirect-pressurization valve means can be operated in accordancewith the following operative conditions: a) completely closed, b)pressurization outlet and discharge outlet in flow communication, inletshut, c) inlet and pressurization outlet in flow communication,discharge outlet closed.
 9. A pressurization system according to claim8, in which the tube of the first hydraulic circuit is connected to aduct for discharging to the reservoir the substantially incompressiblefluid originating from the pressurization device, the discharge ductcomprising discharge-valve means.
 10. A pressurization system accordingto claim 2, the system further comprising a third hydraulic circuitcomprising one or more secondary pressure accumulators which areconnected to the pressure-multiplier means and to the pressurizationdevice in controlled manner in order to reset the piston and/or toactuate the kinematic mechanism for the opening/closure of the removableclosure element.
 11. A pressurization system according to claim 10 inwhich the secondary pressure accumulators are connected, by means of anauxiliary tube comprising, in sequence, valve means and a non-returnvalve, to the space defined between a shoulder of the piston, formed atthe junction point between the two portions of the piston with differentdiameters, and the thicker portion of the housing of thepressure-multiplier means.
 12. A pressurization system according toclaim 11, in which the valve means comprise a first outlet connected tothe auxiliary tube, a second outlet in fluid communication withclosure-control valve means, and a third outlet in fluid communicationwith pin-control valve means, the three outlets being operableindependently.
 13. A pressurization system according to claim 12 inwhich the closure-control valve means in turn comprise a first outlet influid communication with a thrust chamber of a housing of a closurepiston and a second outlet in fluid communication with a return chamberof the housing, and in which the pin-control valve means in turncomprise a first outlet in fluid communication with the thrust chamber(139) of the housing of the pin piston and a second outlet in fluidcommunication with the return chamber of the housing.
 14. Apressurization system according to claim 12 in which the space in thepressure-multiplier means, one or more thrust chambers, and one or morereturn chambers are in flow communication with respective ducts forrecirculating the substantially incompressible fluid to the reservoir.15. A pressurization system according to claim 10, in whichcharging-valve means are provided, disposed downstream of the pump andhaving a first outlet connected to the charging tube, a second outlet influid communication with the secondary pressure accumulators, and athird outlet in fluid communication with a duct for recirculating thesubstantially incompressible fluid to the reservoir, the three outletsbeing operable separately.
 16. A pressurization system according toclaim 1, in which the first hydraulic circuit comprises adirect-pressurization tube in which direct-pressurization valve meansare interposed, the tube putting the primary pressure accumulators intoflow communication with the pressurization device.
 17. A pressurizationsystem according to claim 1, in which the pressurization devicecomprises a housing which has a removable closure element and insidewhich is defined a pressurization chamber for housing one or moreobjects to be processed at high hydrostatic pressures, a piston with aT-shaped cross-section acting in the pressurization chamber, thelarger-diameter end of the piston defining, together with the walls ofthe housing, a chamber filled with a substantially incompressible fluid,and the chamber being connected to the direct-pressurization tube forthe admission of the substantially incompressible fluid to the chamberat high pressure.
 18. A pressurization system according to claim 1 inwhich the pressure accumulators comprise pressure sensors operativelyconnected to the valve means which are connected to the charging tube,to the secondary pressure accumulators, and to the recirculation duct,respectively.
 19. A pressurization system according to claim 1, furthercomprising a pressure multiplier means and wherein the primary pressureaccumulators are charged to approximately 300 bar and secondary pressureaccumulators are charged to approximately 150 bar, and in which theratio between the areas of the end surfaces of the piston of thepressure-multiplier means is approximately
 2. 20. A method ofpressurizing objects to be processed, comprising the steps of: a)providing a pressurization system comprising a first hydraulic circuitin which one or more primary pressure accumulators are connected to apressurization device in a controlled manner in order to permit asubstantially incompressible fluid to be admitted to, or recovered from,the pressurization device at a first pressure, the primary pressureaccumulators being precompressed-gas pressure accumulators, b) puttingthe primary pressure accumulators, which are kept at a first pressure,into flow communication with the chamber of the pressurization device,by means of the first hydraulic circuit, until equilibrium is reached,c) putting the primary pressure accumulators, which are kept at a firstpressure, into flow communication with the chamber of the pressurizationdevice, by means of the second hydraulic circuit, until the secondpressure greater than the first pressure is reached, d) maintaining thesecond pressure in the chamber of the pressurization device for apredetermined period, or bringing about a series of partialdecompressions to a third pressure between the first and secondpressures and compressions to the second pressure, e) returning thepressure in the chamber of the pressurization device to the firstpressure by closure of the indirect-pressurization valve means andopening of the direct-pressurization valve means so as to recoverpotential energy in the form of compressed gas in the primary pressureaccumulators, f) returning the pressure in the chamber of thepressurization device to atmospheric pressure by discharge of thesubstantially incompressible fluid towards the reservoir.
 21. A methodaccording to claim 20 in which the first pressure is approximately 300bar, the second pressure is approximately 600 bar, and the thirdpressure is approximately 500 bar.
 22. A method according to claim 20,in which steps b) to f) are performed within a period of between 10seconds and 20 seconds.